1. Field of the Invention
The present invention relates to voice packet transmission in a gateway system of a network, and in particular to voice packet transmission in a gateway system which can reduce a voice packet delay and a delay jitter generated during voice packet transmission and reception on a network.
2. Description of the Background Art
The number of IP phone users for voice communication has been gradually increased. An IP phone system similar to a computer telephony integration CTI has been widely used. A gateway system connecting a conventional public switched telephone network PSTN to an internet network maps a station number and an IP address of a terminal (computer or IP phone), thereby enabling communication.
Here, a multimedia office communication system (hereinafter, referred to as xe2x80x9cMOCSxe2x80x9d) is exemplified as the gateway system.
FIG. 1 is a connection view of a LAN network in a general MOCS. The MOCS includes a LAN switch board, and converts protocols of the telephone network and the LAN for connection thereof. A plurality of switching hubs SH1-SH6 and a feature server for storing IP addresses and various state information, and performing a call control or other additional functions are connected to the LAN switch board. A local server, an IP phone and a PC phone are connected to each switching hub SH1-SH6. When a call is generated from a specific station, the MOCS transmits a setup message to an IP address corresponding to the call, thereby transmitting/receiving the call.
As a real time traffic LAN environment of voice and image increases, it is important to provide a service of high quality. Especially, a voice packet delay and a delay jitter are important standards for measuring quality of service (hereinafter, referred to as xe2x80x9cQoSxe2x80x9d), and considerably influence on a sound quality of the MOCS.
On the other hand, a few standards are used in the MOCS. A representative standard is 802.1 p/Q. The standard compensates for the sound quality by reducing generation of the voice packet delay and the delay jitter.
FIG. 2 shows a voice packet format of the 802.1 p/Q standard. As shown therein, the voice packet format consists of an Ethernet header, a tag of 4 bytes and a voice packet of the 802.3 p/Q standard. xe2x80x9cPxe2x80x9d in the tag denotes a priority bit. A bit rate of a LAN card using the 802.1 p/Q standard is between 10 and 100 Mbps, identically to a bit rate of a LAN card using the 802.3 p/Q standard.
On the other hand, the LAN card employing the 802.3 p/Q standard cannot read the tag of 4 bytes added to the 802.1 p/Q standard, and accordingly recognizes the voice packet including the tag as an illegal format or does not generate priority. Thus, in order to utilize the 802.1 p/Q standard to reduce generation of the voice packet delay and the delay jitter, the LAN cards of devices connected to the entire network, namely the switch hubs and the LAN card of the PC must be replaced by the LAN cards using the 802.1 p/Q standard.
However, it is inefficient to replace the LAN cards of the 802.3 p/Q standard which are well operated by the LAN cards of the 802.1 p/Q standard. The current MOCS communicates voice of low bit rate (64 kbps) having a real time property in the LAN environment, as in a general key telephone system. As a result, to replace the originally-provided LAN cards is uneconomical.
Especially, in regard to the voice of low bit rate (64 kbps) having the real time property, the MOCS enables communication on the LAN, identically to the general key phone system. Accordingly, to replace the LAN cards does not influence on the bit rate.
Therefore, it is necessary a method for guaranteeing the QoS of the voice traffic without replacing the currently-used LAN cards.
Accordingly, it is a primary object of the present invention to guarantee the quality of service of a voice traffic in LAN environments having different standards.
It is another object of the present invention to reduce a voice packet delay and a delay jitter in LAN environments having different standards.
In order to achieve the above-described objects of the present invention, there is provided a voice packet transmission control device including: a memory, each memory region being divided into a high priority queue and a low priority queue; a central processing unit receiving a priority message, and storing a MAC address and a priority level corresponding to each IP phone in the memory; and a switch storing a voice packet transmitted during communication in the high priority queue, storing a data packet excluding the voice packet in the low priority queue, and firstly transmitting the voice packet stored in the high priority queue, on the basis of the priority levels.
In order to achieve the above-described objects of the present invention, there is provided a voice packet transmission control method including: a step of making a priority message having a priority level; a step of separately storing a voice packet transmitted during communication and a data packet excluding the voice packet, on the basis of the priority level; and a step of firstly transmitting the voice packet in accordance with the priority level.